The present invention relates in general to the detection of the peak values of an AC signal and in specific to the detection and measurement of the response envelope of an AC signal as a function of time both rapidly and with high precision.
Prior methods of obtaining the envelope of an electrical signal rely upon: 1) the use of diode detector circuits incorporating an RC time constant; 2) digitizing the wave form of the signal and performing a mathematical fit to determine each peak value or 3) making measurement directly from an oscilloscope trace.
The first method which employs a diode detector circuit is limited in its accuracy because of the response characteristics of the RC circuit. Since the RC interaction includes a relatively substantial time delay, necessary for the charging and discharging of the capacitor the accuracy of the measurement is limited.
The second method, digitizing of the wave form, require substantial amounts of numerical manipulation of the data and requires a multitude of mathematical operations. This method also requires performing a mathematical “fit” which introduces error into the envelope measurement.
The third method is simply slow and inaccurate because it requires an operator to visually plot the decay response of the signal. All of the above techniques have limitations that are overcome by the new method.
The major improvement introduced by the new method is a large increase in the precision of measurements which results in correspondingly large increases in sensitivity of instruments employing the new technique.